Layered Double Hydroxide with Interlayer Quantum Dots and Laminate Defects for High-Performance Supercapacitor

Owing to the flexible adjustability of laminates, layered double hydroxides (LDHs) can achieve enhanced conductivity and capacitance. However, the regulation of interlayer activity is a great challenge because of the unconquerable charge repulsion between laminates. Herein, a dual-activity design of LDHs is uniquely realized, including laminate defects and interlayer ZnS quantum dots (QDs). Via pre-embedding Zn2+ and controllable vulcanization, ZnS-QDs interpenetrate between CuCo-LDH layers, exposing abundant active sites and widening the layer spacing. Meanwhile, sulfur replaces part of the oxygen on the laminates to form rich oxygen vacancies (CuCo-LDH-S), which does not damage the layered spatial structure and ensures the fast ions/electron transport. Theoretical calculations indicate that the new active centers exhibit higher charge density as compared to CuCo-LDH. Moreover, the copper foam directly provides copper source to ensure that CuCo-LDH-S/ZnS-QDs present a 3D self-supporting structure with ultrastability. Hence, it delivers an ultrahigh capacitance of 7.82 F cm⁻² at 2 mA cm⁻² and 4.43 F cm⁻² at 20 mA cm⁻². The hybrid supercapacitors display an outstanding energy density of 299 µWh cm⁻² at power density of 1600 µW cm⁻², with outstanding capacitance retention of 102.3% and coulomb efficiency of 96.2% after 10 000 cycles.